The invention relates to dental drills, more especially to means for direct illumination of the area in the mouth which is being worked on.
Dental work on teeth and other parts of the oral cavity has to be very accurate and delicate and, therefore, requires a high light intensity beamed onto the area worked upon. The dental surgeon who works in an otherwise dark cavity must be able to direct a strong light beam onto the spot which he drills or grinds, which should not be obstructed by the shadow of his hands or his head.
With primitive equipment this is still the case whereby the dentist has to direct the light rays from an external light source into the mouth by means of a small mirror. This method is highly inconvenient, since it occupies both hands, one hand holding the drilling or grinding tool and the other hand holding the mirror, in addition to the danger of the light-ray between source and mirror being obscured by the hands or the body of the dental surgeon.
For this reason direct illumination was introduced a few years ago, the method comprising the use of optical fibres for transferring a light beam from an external static source to a point just above the drill point or burr inserted into the tool. The light source is generally situated at the central control post whence the light beam is directed into the receiving end of a resilient optical fibre. A first optical fibre extends from the light source as far as the standard connector guided through the rubber hose, at which point it is transferred to a second optical fibre by means of a special connector; the second fibre runs inside the drill along the turbine housing and ends in the drill head while pointing towards the drill point.
Instead of being hampered by these external optical connections to the handpiece in addition to the unavoidable water and air connections, it was found more efficient to locate the energy source inside the handpiece proper; with this object in view I have designed different embodiments of high-speed and low-speed drills, incorporating either a light generator or an electric cell of adequate output.
Israeli Patent Application No. 67784 (corresponding to U.S. Pat. No. 4,561,845) I have disclosed a dental high-speed handpiece which comprises illuminating means in the form of a light bulb attached to its front end so directed as to illuminate the tip of the burr, an electric cell enclosed in the handpiece casing, and wiring connecting the bulb to the cell. The electric cell is enclosed in a centrally positioned chamber in the rear portion of the casing which can be opened, for the purpose of exchanging the electric cell, by removing a cylindrical plug normally inserted into the rear opening of the chamber. This plug contains connectors to the external air and water lines as well as the respective air and water ducts, and carries an electrical contact point urged toward the rear end of the cell. Air and water ducts extend from the ends of the corresponding ducts inside the plug to the front end of the handpiece while running close to the outside wall of the casing, in order to leave room for the chamber containing the cell. Wiring between the cell terminals and the light bulb are, for most of the way, enclosed in the air ducts which serve to supply compressed air to the turbine wheel of the drill and to return exhaust air to the rear of the handpiece.
An improvement of this dental drill is described in Israeli Patent Application No. 69062. Herein a low-speed drill operated by an air motor is provided with illuminating means similar to those incorporated in the handpiece of the high-speed drill. The improvement consists in replacing the electric wiring by the parts of the aluminum casing which are anodized all over, except in those places which should serve for transmitting electric current from one component to another. In this embodiment the ducts carrying air to the air motor, and water to the drill head run along the outer wall of the casing so as to leave sufficient space for the centrally positioned electric cell and air motor.
Both embodiments have proved to be very efficient and suitable for dental drilling, however they still suffer from certain drawbacks which to overcome is the object of the present invention:
1. Each of the aforedescribed handpieces is provided with an electric switch serving to connect the light bulb to the cell as soon as drilling operations are started. This requires additional action of the dental surgeon, it complicates the design and adds to the overall cost of the dental drill.
2. The plug closing the electric cell chamber and carrying the air and water ducts, besides of containing the contact piece to the rear terminal of the cell, is necessarily sealed by gaskets or O-rings from the rest of the casing, in order to prevent water from entering the cell chamber and from short-circuiting the illumination circuit. Replacement of the electric cell by removal and reinsertion of the plug requires a relatively expensive system of coordinating the ducts inside the plug and inside the casing, which adds to the difficulties in preventing water from leaking into the cell chamber.